The many faces of graphene as protection barrier. Performance under microbial corrosion and Ni allergy conditions

In this work we present a study on the performance of CVD (chemical vapor deposition) graphenecoatingsgrownandtransferredonNiasprotectionbarriersundertwoscenariosthatleadto unwantedmetalionrelease,microbialcorrosionandallergytestconditions. Thesephenomenahavea strongimpactindifferentfieldsconsideringnickel(oritsalloys)isoneofthemostwidelyusedmetals in industrial and consumer products. Microbial corrosion costs represent fractions of national gross product in different developed countries, whereas Ni allergy is one of the most prevalent allergic conditions in the western world, affecting around 10% of the population. We found that grown graphene coatings act as a protective membrane in biological environments that decreases microbial corrosion of Ni and reduces release of Ni2+ ions (source of Ni allergic contact hypersensitivity) when incontactwithsweat. Thisperformanceseemsnottobeconnectedtothestrongorbitalhybridization that Ni and graphene interface present, indicating electron transfer might not be playing a main role in the robust response of this nanostructured system. The observed protection from biological environment can be understood in terms of graphene impermeability to transfer Ni2+ ions, which is enhanced for few layers of graphene grown on Ni. We expect our work will provide a new route for application of graphene as a protection coating for metals in biological environments, where current strategies have shown short-term efficiency and have raised health concerns.